FAA Aviation Mechanic General (AMG)Fundamentals of Electricity and ElectronicsHard
An aircraft's AC electrical system operates at a frequency of 400 Hz. What is the period of one complete cycle of this AC waveform?
- A25 milliseconds
- B2.5 milliseconds
- C0.4 milliseconds
- D40 milliseconds
Show answer & explanationAnswer & explanation
Correct answer: B. 2.5 milliseconds
The period of an AC waveform is the reciprocal of frequency: T = 1/f. For a 400 Hz system, T = 1/400 = 0.0025 seconds, which equals 2.5 milliseconds.
Why the other options are wrong
- A. This value is ten times too large, likely a decimal error.
- C. This value is ten times too small for the correct calculation.
- D. This value corresponds to a much lower frequency, not 400 Hz.
Frequency-Period Relationship
Period (T) is the time for one complete AC cycle and is the mathematical reciprocal of frequency (f): T = 1/f.
- Formula: T = 1/f (seconds)
- Aircraft AC systems commonly use 400 Hz
- Higher frequency means shorter period
Memory trick: Frequency and period are reciprocal dance partners — one up, the other down.